It could the added heat created by the high intensity lights used for a reef tank that did it. Where they Metal Halides or T5H0's?
One of the reasons that many who do reef tanks do not use canister filters, the lighting could in theory melt the hoses and cause them to slip off.
When I hooked up mine, I softened the hoses in a cup of boiling water, pushed them on and now the only physically way to remove them from the barbs would be to cut them, they molded very tightly.
80F is not nearly hot enough to cause the hoses to collapse. 212F is the temperature of boiling water and even then it took a few minutes of being immersed before it became soft enough to manipulate easily.